1. Field of the Invention
The present invention relates to a light-pattern illuminating apparatus and a light-pattern illuminating method which are used in an image recording apparatus in which a light pattern corresponding to image information is applied to an image receiving element and an image represented by image information is recorded on the image receiving element, or in an image reading apparatus in which an image represented by image information is read by the image receiving element.
2. Description of the Related Art
In recent years, research and development have been advancing concerning a technology in which, in an image recording apparatus such as a photographic printer and an image reading apparatus such as a scanner, surface exposure is effected by using a light-conductive type liquid-crystal light bulb used in the field of color television projectors, for example.
As shown in FIG. 16, Japanese Patent Application Laid-Open (JP-A) No. 7-270746 discloses a technique relating to an image recording apparatus which is capable of recording an image with high resolution at high speed by using a general-purpose photosensitive material.
In this image recording apparatus, a pattern of light 230 corresponding to an image of blue (B) represented by image signal Q is projected from a CRT 221 and is applied and written to a spatial light modulating element 223. Then, reading light 240 is made emergent from a halogen lamp 227, and this reading light 240 is transmitted through a B filter 228, is made incident upon a prism beam splitter 224, is reflected by the prism beam splitter 224, and is made incident upon the spatial light modulating element 223.
The reading light 240 is modulated and reflected by the spatial light modulating element 223 in correspondence with the written light pattern, is again transmitted through the spatial beam splitter 224 as recording light 250, and is applied to a photosensitive material 226 through a projection lens 225. Then, the photosensitive material 226 is sensitized by the recording light 250, thereby recording an image of B. Thereafter, light patterns of green (G) and red (R) are consecutively recorded on the photosensitive material 226 in a similar manner.
According to this image recording apparatus, a light pattern corresponding to an image to be recorded is temporarily written to the spatial light modulating element 223, reading light is applied to the spatial light modulating element 223 to read the light pattern written to the spatial light modulating element 223, and the light pattern thus read is recorded on the photosensitive material. Therefore, a high-resolution light pattern can be written to the spatial light modulating element 223 without making the luminance high for the CRT 221 used for writing a light pattern. At the same time, if the amount of reading light for reading the light pattern is increased, a high-resolution image can be recorded on the photosensitive material in a short time. Furthermore, after the image to be recorded is temporarily written to the spatial light modulating element 223 as a light pattern, the light pattern is read by the reading light, and is recorded on the photosensitive material. Therefore, the problem of so-called reciprocity law failure does not occur.
Thus, technology is conventionally known in which a light pattern corresponding to an image to be recorded is written to the spatial light modulating element by making use of a surface illuminant such as a CRT, reading light from the prism beam splitter is reflected (modulated) in correspondence to the written light pattern, and individual images of R, G, and B are recorded on the photosensitive material, thereby obtaining a color image.
As a technique relating to the present invention, a technique is described in Japanese Patent Application Laid-Open (JP-A) No. 8-240867.
However, with the technique described in Japanese Patent Application Laid-Open (JP-A) No. 7-270746, an image to be recorded is written to a light modulating layer of the spatial light modulating element, which consists of a liquid crystal or the like which is not provided with the features of a memory, by means of a surface illuminant as a light pattern. The written light pattern is read for a predetermined duration irrespective of the write scanning period by means of the reading light of the three colors, R, G, and B, respectively, and the photosensitive material is exposed by the light patterns thus read. Therefore, there have been problems in that deviations in color tone and density unevenness occur periodically in reproduced images obtained, and that places where deviations in color tone and density unevenness occur are not fixed, so the finished quality of a plurality of reproduced images obtained from identical image signal Q is not the same.
Hereafter, referring to FIGS. 17A to 17F, a detailed description will be given of the causes of the occurrence of deviations in color tone and density unevenness in the technique described in Japanese Patent Application Laid-Open (JP-A) No. 7-270746.
FIG. 17A is a diagram in which scanning lines of the CRT 221 are viewed from the spatial light modulating element 223 side. To simplify the description, it is assumed that the CRT 221 is an interlaced type, and that positions of the first and last pixels which form scanning lines are respectively located at points P and Q. FIG. 17B is a diagram in which scanning lines of an image written to the spatial light modulating element 223 are viewed from the photosensitive material 226 side. If points on the spatial light modulating element 223 corresponding to points P and Q on the CRT 221 are assumed to be P' and Q', respectively, and if the reflectance at point P', as viewed from the photosensitive material 226 side, is measured by a measuring instrument, the reflectance fluctuates as shown in FIG. 17D. Incidentally, FIG. 17C shows the period (period of vertical scanning) in which a beam of the CRT 221 scans from point P' to point Q'. In addition, point P' shown in FIG. 17C corresponds (assumes the same timing) to rise starting point P' in the fluctuation of the reflectance shown in FIG. 17D.
In contrast, in the technique described in Japanese Patent Application Laid-Open (JP-A) No. 7-270746, in a case where a plurality of identical reproduced images are recorded on the photosensitive material 226, the exposure of R for recording, for instance, a first reproduced image starts at timing t.sub.RS1 and ends at timing t.sub.RE1 (see FIG. 17E), and the exposure of R for recording a second reproduced image starts at timing t.sub.RS2 and ends at timing t (see FIG. 17F). Thus, although exposure time t.sub.R for R is fixed, timings at which the exposure of R starts and ends are not fixed with respect to fluctuations of reflectance shown in FIG. 17D. The same also applies to G and B.
Accordingly, since, as viewed from the photosensitive material 226 side, an integrated value (or average value) of reflectance is not fixed during the period of exposure of the photosensitive material 226, deviations in color tone and density unevenness. For this reason, the finished quality of the plurality of reproduced images recorded on the photosensitive material is not identical.